Process for producing multilayer color negatives containing masking images for colorcorrection purposes



Feb. 13, 1951 J 5. FRIEDMAN 2,541,

PROCESS FOR PRODUCING MULTILAYER COLOR NEGATIVES CONTAINING MASKINGIMAGES FOR COLOR CORRECTION PURPOSES Filed Nov. 18, 1947 F G 1 EXPOSEDAND COLOR DEVELOPED MULT/LAYER A 4 COLOR FILM NEGATIVE COLOR IMAGES ANDN P0 IL NEGATIVE SILVER H 2 5 VER IMAGES I 1. BLEAGHED 2. EXPOSED TOAcommon/:0 QUANTITY OF WHITE LIGHT B /4 NEGATIVE cow/e m IMAGES ANDSILVER 4/ LA TENT SOSgT/VE BROMIDE I I SILVER ALI E IMAGES DEVELOPED INDEVELOPER CONTAINING POTASSIUM /0D/DE I /4 UNDEVELOPED NEGATIVE GOLORSILVER HAL/DE IMAGES AND SILVER /2 BROMIDE POSITIVE S/L VER MA SK/NG IMAGES F/XAT/ON D /4 POSITIVE SILVER I [3 MASK/N6 IMAGES NE GA TI l E GOLOR I 2 IMAGES INVENTOR JOSEPH S. FRIEDMAN ATTORNEYS Patented Feb. 13,1951 PROCESS FOR PRODUCING MULTILAYER COLOR NEGATIVES CONTAINING MASK-ING IMAGES FOR COLOR CORRECTION PURPOSES Joseph S. Friedman, JohnsonCity, N. Y., assignor to General Aniline & Film Corporation, New York,N. Y., a corporation of Delaware Application November 18, 1947, SerialNo. 786,810

2 Claims.

This invention relates to color photography, and more particularly to aprocess of producing multi-layer color ne atives containing maskingimages in the cyan and magenta layers for color correction purposes.

In the production of color prints from multilayer color negatives, thecolor negative consists of yellow, magenta, and cyan images in thedifferent layers. The cyan image represents the red, the magenta imagethe green, and the yellow image the blue record of the original subject.C'olor positive prints or transparencies may be obtained from such colornegatives by direct printing onto a multi-layer color positive film orpaper, or by making color separation negatives which are used for makingthe color positive prints. These color negatives do not, as a rule,completely satisfy the spectral requirements for trichromatic colorreproduction. For instance, the magenta colored image, formed by theimposition of green light upon the green sensitive layer, records thegreen densities. This image should transmit the blue and the redprimaries, completely. To the extent to which it absorbs blue light, itsuperimposes a pattern of the green densities uponv the blue, withconsequent color falsification. This color falsification makes itselfmanifest when the color negative is to be printed. That part of theexposure which is due to blue light, and which should form a record onlyof the image in the yellow layer in the negative, forms a record of theyellow image admixed with the record of the magenta. The image in theblue sensitive part of the copy mamrial is, therefore, very impure, andserious color degradation results.

It ispossible to overcome this defect if procedures are devised toregister a pattern of the magenta dye image, equal in intensity to thedegree to which the magenta dye absorbs blue light, but opposite incharacter, with the yellow dye images. In a similar manner the cyan dyeimage can be corrected for its blue absorption. These masks or modifyingimages can be yellow in color, as suggested by the prior art, or theycan be a neutral gray, composed of dye or silver.

Numerous methods have been proposed for making corrections in these dyeimages. Generally, these methods are characterized by the fact that themask is on a separate piece of film, and must be registered with theoriginal by manual or mechanical means. This creates problems ofregistry arising from the dimensional variations of film as it ages, andproblems of definition arising from lack of optical contact betweenoriginal and mask, Newton rings, etc. It is desirable, therefore, tohave the mask integral with the original. To accomplish this, it hasbeen proposed to place an auxiliary emulsion layer within the pack inwhich themask could be formed. While this gives a desirable result, itintroduces complications into the structure and the preparation of themonopack material. Since the masking image is opposite in character tothe one that it is desired to modify, emulsions with special propertieshave to be used.

To eliminate this complication, it was proposed in British Patent541,266 to utilize the residual silver-halides in the emulsion after thelatent image had been processed to a dye image, and to convert theresidual halides, after a proper exposure, into a black and white silvermask. The procedure disclosed, to accomplish the formation of a mask,involved the treatment of the film after negative color development in ableach bath to convert the silver to silver chloride, removal of thesilver chloride by treatment with ammonia or ammonium sulfite, exposureof the untouched residual silver bromide to white light, and developmentin an M. Q. developer that yields a silver image. When processed in thismanner, there are formed silver images in each of the layers of thecolor film. This may be desirable under certain conditions, but forcertain purposes the presence of a mask representing an image of theyellow dye pattern is harmful and undesirable. This was recognized bythe British patentee and he specifically states in his specificationsthat the bleach, to be used to efiect a conversion of the silver tosilver chloride, be of such a mild nature that it does not destroy thecolor sensitivities of the green and red sensitive layers. Aftertreatment with such a mild bleach solution, it becomes possible toselectively expose the red and/or green sensitive layers, so that.masking images are formed only in these parts.

The restriction that a bleach be used that is so mild that it does notdestroy the color sensitivity of the green and red layers, severelylimits the operator using the material and the manufacturer who makesit. The patentee cites a number of sensitizing agents that could beused, which will not be destroyed by the extremely mild agents hementions. But, generally, subjecting an optically sensitized film to theaction of an oxidizing agent reduces the color sensitivity of thatmaterial almost to the vanishing point. To

emulsion grain layers. probably difiuses much faster than the potassiumiodide.

:de'eper sections of the emulsion layers. all developing action isstopped in the yellow or uppermost layer, but not in the cyan andmageneflect a selective exposure in the green and red sensitive layerswould require such long durations as to make the procedure impracticalunless special sensitizers be used which are not so affected.

Another method, recently proposed, consists of forming. masking imagesin the original green and red sensitive layers by a reversal processing.The procedure proposed, to accomplish the formation of a mask, is tocolor develop the exposed multilayer color film and then subject it tothe action of a special fixing bath whose penetration into the depth ofthe emulsion layer can be controlled and the fixing action thereoflimited to the uppermost blue sensitive layer. By this procedure, theresidual silver-halides in the blue sensitive layer are removed and canno longer be used to form a masking image, whereas the residualsilver-halides in the green and red sensitive layers are substantiallyunafiected and masking images are formed in these layers upon subsequentexposure and development.

The use of a controlled fixing'bath, whose action is limited only to agreen layer, presents a complex problem. For instance, it is extremelydifiicult to prepare such a bath which will have no effect whatsoeverupon the residual silverhalides in the other two layers, due to the com--plication of maintaining a sharp line of penetration as the bathsolution becomes absorbed or diffuses through the gelatin.

It'is, therefore, an object of the present invention to provide a methodfor obtaining, in subtractively multi-layer colored photographic colornegative materials, masking images composed of silver which correct forthe color deficiencies of the cyan and magenta dye images thereof.

A further object is to provide a method for obtaining color correctedcolor negative materials wherein the color correction is integrallybound with the cyan and magenta dye images. Other objects and advantagesof this invention will be apparent by reference to the foregoingspecification, in which its preferred details and embodiments aredescribed.

The foregoing objects are accomplished by developing an exposed,color-developed, bleached, "and re-exposed color negative film in theusual black and white developer containing a small quantity of potassiumiodide which will govern the depth at which development will start. Thepotassium iodide does not function as a developer, or fog-inhibitingagent. Its function is to control the extent below the top surface ofthe emulsion ,layer at which development will start.

During this controlled depth development, the potassium iodidedesensitizes the upper strata of the The developing solution Hence, inthe deeper sections of the emulsion layers, i. e., the magenta and cyanlay- .ers, the developing solution acts normally as though the potassiumiodide were absent, since by the time the development action starts,said potassium iodide will have not penetrated to the In short,

this controlled depth development, there is achieved the formation ofcolor-correcting silver images in the magenta and cyan layers.

4 In practicing the present invention, the process involved comprisesthe following steps:

1. Exposure of the color negative film.

2. Development of the latent images with a color developer.

3. Short-stopping with an acid bath and washing in running water.

4. Bleaching, i. e., converting, of all the silver negative images andany other silver, such as the colloidal silver that may be present inthe yellow filter and anti-halation layers, into silver bromide by anybleach bath which does not impair the dye images already present.

5. Exposure of the film to a controlled quantity of White light.

6. Development of the masking images by means of a black and whitedeveloper, containing from 0.02 to 0.4 gram of potassium iodide perliter of developer for a period of time ranging from 2 to 10 minutes.

7. Fixation of the unused silver bromide.

8. Washing and drying in the usual manner.

It is to be noted that, during the bleaching of the exposed andcolor-developed film, the bleach bath reconverts the negative silverimages to silver bromide and these newly formed silver bromide grainsare light-sensitive, so that upon reexposure and development with adeveloping agent containing potassium iodide, the latent images ofsilver bromide grains form silver images. The sensitivity of thereformed silver bromide grains is very much less than the sensitivity ofthe residual silver bromide left after cclordevelopment. Hence, amplesensitivity differential exists between the silver bromide formed by therehalogenation of the negative silver image and the residual silverbromide to allow the formation of latent images only in the residualsilver bromide.

It should be pointed out that, although any black and white developer towhich potassium iodide has been added may be employed, 1 prefer thosedevelopers which contain hydroquinone, or p-aminophenol as the reducingagent, because they have the least effect upon the dye images formed inthe three layers.

The foregoing description of my invention will be more apparent from thefollowing example which is set forth merely to illustrate and should notbe construed as a limitation thereof.

Example A multi-layer photographic color film, such as preparedaccording to U. S. Patents 2,179,228; 2,179,239;-2,l86,849; 2,220,187and 2,357,388, was exposed to a colored object and then developed for 15minutes in a color developer of the following composition:

portions of the multi-layer film. The color developed film was thenshort-stopped in a 1% solution of acetic acid containing 1% sodium.acetate, .and washed'for 10 minutes in running water.

.After washing, all of the metallicsilver in all Disodium monopotassiumferricyanide grams 100.0 Potassium bromide do 15.0 Disodium phosphate do400 Sodium sulfate do 22.5 Water to make liters 1 depth developer of thefollowing composition:

p-Aminophenol grams 5.0 Sodium sulfite do 40.0 Sodium metaborate do 40.0Potassium bromide do 8.0 Potassium iodide do 0.4 Water to make liters 1The developed film was then washed, fixed, and dried in the usualmanner.

During the masking development, the exposed silver-halides present inthe cyan and magenta layers were reduced to metallic silver, therebyforming in each such layer a masking image composed of metallic silverto provide for color correction in printing. No such development tookplace in the yellow (uppermost) layer.

The procedure of the foregoing example has the advantage over othermasking methods in that it cuts down the number of processing steps andreduces the time of processing.

In the accompanying drawing, Figure 1 is a flow diagram representingenlarged sectional views of a film showing the method of forming amasked image according to my invention. Views A, B, and C of Figure 1illustrate the changes taking place in the film during the variousstages of processing.

As shown in the figure, I 0 is a transparent base or support havingsuperposed thereon, layers ll,

l2, and I4 containing cyan, magenta, and yellow color images,respectively. Layer 13 represents a filter layer.

A illustrates a section of the multilayer color .film which has beenexposed and color reveloped.

B illustrates the same multilayer color film after it has been bleachedand exposed to a controlled quantity of white light. C illustrates thesame multilayer color film after it has been developed in a developercontaining potassium iodide. D illustrates the'same multilayer colorfilm after fixation.

It will be noted that masking images consisting to those skilled in theart which, however, do not depart from the spirit and nature of thisinvention and I do not intend to be limited in the patent granted exceptas required in the follow ing claims.

I claim:

1. In the production of subtractively colored negatives with correctionprinting masks, integrally bound therein, for multi-layer filmcomprising an impermeable support having superimposed silver-halideemulsion layers containing color-formers and being respectivelysensitized to the blue, green, and red regions of the spectrum, the bluesensitive layer being outermost, by exposing said multi-layer film to acolored object, color developing, whereby yellow, magenta, and cyanimages are formed in the respective layers, andrehalogenizing themetallic silver by bleaching and re-exposing, the improvement whichcomprises exposing all layers of the bleached film to substantiallywhite light to permit the formation of latent images only in theresidual silverhalide without the formation of latent images in thesilver-halide obtained by bleaching, and developing the re-expo-sedsilver-halide layers to positive silver images only in the magenta andcyan layers in a black and white developer containing from 0.02 to 0.4gram per liter of developer of a depth controlling reagent consisting ofpotassium iodide.

2. In the production of subtractively colored negatives with correctionprinting masks, integrally bound therein, for multi-layer filmcomprising animpermeable support having superimposed silver-haiioleemulsion layers containing color-formers and being respectivelysensitized to the blue, green and. red regions of the spectrum, the bluesensitive layer being outermost, by exposing said muiti-layer mm to acolored object, color developing, whereby yellow, magenta, and cyanimages are formed in the respective layers, and renalogenizing themetallic silver by bleaching, and re-exposing, the improvement whichcomprises exposing all layers of the bleached film to substantiallywhite light to perbleaching, and developing the re-exposed silverhalidelayers to positive silver images in the magenta and cyan layers in ablack and white developer of the following composition:

p-Aminophenol grams 5.0 Sodium sulfite do 40.0 Sodium metaborate do 40.0Potassium bromide do 8.0 Potassium iodide do 0.4 Water to make liters 1JOSEPH S. FRIEDMAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,137,785 Sanders- Dolgoruki etal. Nov. 22, 1938 2,153,698 Reindorp Apr. 11, 1939 2,159,600 Murray eta1. May 23, 1939 2,203,653 Evans June 4, 1940 2,431,996 Duerr et a1.Dec. 2, 1947

1. IN THE PRODUCTION OF SUBTRACTIVELY COLORED NEGATIVES WITH CORRECTIONPRINTING MASKS, INTEGRALLY BOUND THEREIN, FOR MULTI-LAYER FILMCOMPRISING AN IMPERMEABLE SUPPORT HAVING SUPERIMPOSED SILVER-HALIDEEMULSION LAYERS CONTAINING COLOR-FORMERS AND BEING RESPECTIVELYSENSTITIZED TO THE BLUE, GREEN, AND RED REGIONS OF THE SPECTRUM, THEBLUE SENSITIVE LAYER BEING OUTERMOST, BY EXPOSING SAID MULTI-LAYER FILMTO A COLORED OBJECT, COLOR DEVELOPING, WHEREBY YELLOW, MAGENTA, AND CYANIMAGES ARE FORMED IN THE RESPECTIVE LAYERS, AND REHALOGENIZING THEMETALLIC SILVER BY BLEACHING AND RE-EXPOSING, THE IMPROVEMENT WHICHCOMPRISES EXPOSING, THE IMPROVEMENT WHICH TO SUBSTANTIALLY WHITE LIGHTTO PERMIT THE FORMATION OF LATENT IMAGES ONLY IN THE RESIDUALSILVERHALIDE WITHOUT THE FORMATION OF LATENT IMAGES IN THE SILVER-HALIDEOBTAINED BY BLEACHING, AND DEVELOPING THE RE-EXPOSED SILVER-HALIDELAYERS TO POSITIVE SILVER IMAGES ONLY IN THE MAGNETA AND CYAN LAYERS INA BLACK AND WHITE DEVELOPER CONTAINING FROM 0.62 TO 0.4 GRAM PER LITEROF DEVELOPER OF A DEPTH CONTROLLING REAGENT CONSISTING OF POTASSIUMIODIDE.